Connecting structure to cell of voltage detecting connector and fuel cell

ABSTRACT

A voltage detecting connecting structure and fuel cell has connectors which are in contact with terminals connected to the fuel cell. An embodiment of the fuel cell includes first cells which have the terminals at an anode and a cathode respectively, and second cells which have terminals in neither an anode plate nor a cathode, stacked alternately. Another embodiment of the fuel cell includes first cells with terminals provided only to anode sides thereof, and second cells with terminals provided only to cathode sides thereof, the first cells being stacked from one end of the fuel cell and the second cells being stacked from the other end of the fuel cell.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a connecting structure to a cell of anelectrical voltage detecting connector which is connected to a fuel cellconstituted by laminating plural cells having an anode and a cathode,for detecting electrical voltage of the cell, and to a fuel cell.

Priority is claimed on Japanese Patent Application No. 2004-235153,filed Aug. 12, 2004, and Japanese Patent Application No. 2004-235154,filed Aug. 12, 2004, the contents of which are incorporated herein byreference.

2. Description of Related Art

In recent years, fuel cells are attracting attention as a new source ofpower, such as for an automobile. In general, a fuel cell consists of amembrane electrode architecture (MEA) in which an anode electrode(negative electrode) and a cathode electrode (positive electrode) aredisposed on either side of a solid polymer electrolyte membranerespectively, and a pair of separators which contain the membraneelectrode architecture therebetween. When this fuel cell is operated togenerate electricity, it generates an electrochemical reaction bysupplying gaseous fuel (for example, hydrogen gas) to the anodeelectrode of the fuel cell, and supplying oxidizing gas (for example,air containing oxygen) to the cathode electrode. Since only harmlesswater is generally generated when generating electrical power, the fuelcell attracts attention from a viewpoint of influence on the environmentor use efficiency.

Incidentally, it is difficult to obtain electric power sufficient todrive an automobile from one fuel cell. It has been investigated tomount a fuel cell which has a stack structure in which plural cells eachof which is formed by interposing a membrane electrode architecturebetween a pair of separators are layered, in an automobile, such thatsufficient electric power to drive the automobile can be supplied.

In this case, in order to monitor whether a cell which constitutes afuel cell is generating electricity normally, it is very important todetect the voltage of the cell. From such a viewpoint, a fuel cellprovided with terminals for measuring voltage is proposed.

For example, patent document 1 (Japanese Unexamined Patent Application,First Publication No. H09-283166) discloses technology in which acircular hole is formed in the carbon plate of each cell, and one end ofan output terminal is connected to the circular hole using a bananaclip, and another end of an output terminal bundle with a voltagemeasuring apparatus is connected through a connector.

Moreover, patent document 2 (Japanese Unexamined Patent Application,First Publication No. 2003-86219) discloses technology of clipping aterminal holder which holds terminals disposed on separators of cells ofa fuel cell, thereby making the terminals unmovable.

Moreover, cross sections of the principal part of a fuel cell and of avoltage detecting connector which is connected to the fuel cell areshown in FIG. 5. As shown in this figure, a fuel cell 30 consists of apredetermined number (in this case, n) of cells 31, which are stacked.Each cell 31 is interposed between separators 33 and 34 in a membraneelectrode architecture 32. In each cell 31, terminals 35 and 36 formeasuring electrical voltage are disposed on the separator 33 at ananode electrode side and the separator 34 at a cathode electrode side,respectively. A cell connecting device 39 is connected to the fuel cell30 thus constituted. The cell connecting device 39 is equipped with apredetermined numbers of connectors 37 and 38, whereby the electricalvoltage of the separators 33 and 34 disposed at the terminals 35 and 36can be detected by contacting the connectors 37 and 38 with theterminals 35 and 36, thereby, detecting electrical voltage in each cell.

However, hitherto, there were the following problems. That is, in theconventional art, as explained above, referring to FIG. 5, in general,each terminals 35 and 36 of the fuel cell 30 are arranged in series inthe same position when they are looked at from a direction of layering.However, in order to mount the fuel cell 30 in a vehicle etc., it isrequired to reduce the thickness of each cell 31 to as thin as possible,and the gap between the terminals 35 and 36 tends to become narrowinevitably in connection with this.

As a result, when the terminals 35 and 36 are arranged in series, thegap between the terminals 35 and 36 becomes narrow, and there ispossibility of interference with the connection of the connectors 37 and38, if for example, the gap between the cell connecting devices 39provided with the connectors 37 and 38 cannot be maintainedsufficiently, and as a result, the cell connecting devices 39 come intocontact with each other, etc.

Moreover, since it is necessary to stack a lot of cells 31 in order toobtain a required output in the case in which the fuel cell 30 ismounted in a vehicle, if the terminals 35 and 36 are disposed on all ofthe separators 33 and 34 of each cell 31, the weight will increase to anextent that cannot be ignored because of the terminals 35 and 36, andthe cost will increase.

Next, cross sections of the principal part of a fuel cell and of avoltage detecting connector which is connected to the fuel cell areshown in FIG. 10, as is disclosed in, for example, the patent document 3(Japanese Unexamined Patent Application, First Publication No.2002-352820). As shown in this figure, a fuel cell 130 consists of apredetermined number (in this case, n) of cells 131, which are stacked.Each cell 131 is interposed between separators 133 and 134 in a membraneelectrode architecture 132. In each cell 131, a terminal 135 formeasuring electrical voltage is disposed on a separator 133 at an anodeelectrode side. A cell connecting device 139 is connected to the fuelcell 130 thus constituted. The cell connecting device 139 is equippedwith a predetermined number of connectors 137, whereby the electricalvoltage of the separators 133 disposed at the terminals 135 can bedetected by contacting the connectors 137 with the terminals 135,thereby detecting electrical voltage in each cell.

However, there are the following problems in the prior art. That is,hitherto, as explained referring to FIG. 10, because a terminal isdisposed on the separator of one electrode (for example, an anodeelectrode), in order to detect the cell voltage of one cell, themonitoring is performed ranging over the separator of the electrodeshared with the adjoining cell. As a result, in the case of detectingthe cell voltage of the end cell of a stacked body in which plural cellsare stacked, there is no cell adjoining thereto, and it is impossible todetect the cell voltage of the end cell. Therefore, in order to detectthe cell voltage of the end cell, as shown in FIG. 10, it is necessaryto dispose a cover plate (dummy separator) 140 having the same shape asa separator (separator at the side of an anode electrode) 134, on theend of the stacked body of cells and to dispose a terminal 141 for aconnector 142 on the cover plate 140. Thus, it is necessary to disposeseparately, a separator, a terminal, and a connector, which are notrelated to power generation, and the number of parts increases, therebyincreasing cost, stacking width, and weight.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide aconnecting structure to the cell of a voltage detecting connector whichcan prevent increase in weight due to terminals and increase of cost,while detecting all of the cell voltages and maintaining gaps betweenterminals, and a fuel cell.

In addition, it is another object of the present invention to provide aconnecting structure to the cell of a voltage detecting connector whichcan detect the cell voltage at both ends of the stacked body, whileprevent increase in the number of parts, cost, stacking width, andweight, and a fuel cell.

The first aspect of the present invention is a connecting structurebetween a connecting apparatus for a fuel cell and a fuel cell (forexample, a fuel cell 1, in the embodiment) having a structure in whichfirst cells (for example, first cells 2 a in the embodiment) havingterminals (for example, terminals 6 and 7, in the embodiment) providedto cathodes (for example, cathode electrodes 12, in the embodiment) andanodes (for example, anode electrodes 11, in the embodiment) thereof,and second cells (for example, second cells 2 b, in the embodiment)having terminals provides to neither cathodes nor anodes thereof arestacked in alternation, characterized in that the connecting apparatusand the fuel cell are electrically connected by contacting the terminalswith the connectors which are disposed at positions corresponding to theterminals, in the connecting apparatus.

According to the first aspect of the present invention, since twoopposed electrodes of two cells adjoining in the stacking direction havethe same electric potential, the anodes or the cathodes of the secondcell in the fuel cell have the same electric potential as the anodes orthe cathodes of the first cells which adjoin the second cells in thestacking direction. Therefore, since the voltage of the second cellswith no terminals can be obtained from the electric potential of theanodes or the cathodes of the first cells which adjoin the second cellsin the stacking direction, it is possible to maintain high detectingaccuracy equivalent to the case in which terminals are disposed on theanodes and the cathodes of all of the cells. Moreover, compared to thecase in which terminals are disposed on the anodes and the cathodes ofall of the cells, the total number of terminals can be reduced to beapproximately half, and hence, it is possible to maintain sufficientgaps between the terminals, thereby enabling the connectors to beconnected to the terminals smoothly. In addition, it is possible tolower increase of weight caused by the terminals as well as cost.

The second aspect of the present invention is a connecting structureaccording to the first embodiment, in which the first cells are disposedon at least both ends of the fuel cell, and the connectors are connectedto the fuel cell consisting of the first cells and the second cellswhich are stacked alternately from both ends of the fuel cell.

According to the second aspect of the present invention, since the firstcells are disposed on both sides of the fuel cell, and the first cellsand the second cells are stacked alternately from both ends, it ispossible to know certainly the voltage of the first cells which aredisposed on both ends and the second cells which adjoin the first cells,and as a result, it becomes possible to detect the voltage ranging overall of the cells, while lowering increase of weight due to the terminalsand also cost, thereby maintaining the detecting accuracy of the cellvoltages to be equivalent to the case of disposing terminals to anodesand cathodes of all of the cells. In addition, by disposing the cellshaving terminals on both ends, it becomes unnecessary to use specialdummy cells.

The third aspect of the present invention is a fuel cell including:first cells provided with terminals to each of anodes and cathodesthereof, and second cells provided with no terminals to neither anodesnor cathodes thereof, in which the first cells and the second cells arestacked alternately.

According to the third aspect of the present invention, since thevoltage of the second cells with no terminals can be obtained from theelectric potential of the anodes or the cathodes of the first cellswhich adjoin the second cells in the stacking direction, substantiallyall of the cell voltages can be detected, and thereby it is possible tomaintain high detecting accuracy equivalent to the case of disposingterminals to anodes and cathodes of all of the cells. Moreover, comparedto the case of disposing terminals to anodes and cathodes of all of thecells, the total number of terminals can be reduced to be approximatelyhalf, and hence, it is possible to maintain the gaps sufficientlybetween the terminals, which enables the connectors to be connected tothe terminals smoothly. In addition, it is possible to lower increase ofweight caused by the terminals as well as cost.

The fourth aspect of the present invention is a fuel cell according tothe third aspect of the present invention, in which the first cells aredisposed to at least both ends in the direction of stacking, and thefirst cell and the second cell are stacked alternately from both ends.

According to the fourth aspect of the present invention, since thevoltages of the first cell which are disposed to both ends and thesecond cells which adjoin the first cells in the stacking direction canbe certainly known, it becomes possible to detect the voltages rangingover all of the cells, while lowering increase of weight caused by theterminals as well as cost, and as a result, it is possible to maintaindetecting accuracy at a level which is equivalent to the case ofdisposing terminals to anodes and cathodes of all of cells. Moreover, bydisposing the cells with terminals on both ends, it becomes unnecessaryto use special dummy cells.

The fifth aspect of the present invention is a connecting structurebetween a connecting apparatus for a fuel cell and a fuel cell (forexample, the fuel cell 1 in the embodiment) having a structure in whichfirst cells (for example, the first cell 2 a in the embodiment) havingterminals (for example, the terminal 6 in the embodiment) provided onlyto anodes (for example, an anode electrode 111) thereof, and secondcells having terminals provided only to cathodes (for example, thecathode electrode 12 in the embodiment) thereof are stacked inalternation, characterized in that the connecting apparatus and the fuelcell are electrically connected by contacting the terminals with theconnectors (for example, the connectors 8 and 9 in the embodiment) whichare disposed at positions corresponding to the terminals, in theconnecting apparatus.

According to the fifth aspect of the present invention, since mutuallyopposing electrodes of the cells adjoining each other in the stackingdirection have the same electrical potential, the anodes or the cathodesof a cell have the same electrical potential as in the anodes or thecathodes of the cells which oppose to the cell. Since only the firstcells which have terminals on the anodes only are stacked from theanode-side end, the electrical potentials of the anodes of the firstcells which are detection targets can be obtained from the terminalswhich are disposed on the anodes, whereas the electrical potentials ofthe cathodes of the first cells can be obtained from the terminals whichare disposed on the anodes of the cells which adjoin the cells, and fromthese the voltages of the first cells, which are detection targets, canbe obtained. On the other hand, since the second cells, which have aterminal only at the cathode, are stacked from the cathode-side end, theelectrical potentials of the cathodes of the second cells which aredetection targets can be obtained from the terminals which are disposedon the cathodes, whereas the electrical potential of the anodes of thesecond cells can be obtained from the terminals which are disposed onthe cathodes of the cells which adjoin the cell, and from these thevoltages of the second cells, which are detection targets, can beobtained. Thus, it is possible to detect the cell voltage at both ends,without disposing parts which have nothing to do with electricgeneration, such as dummy separators, terminals, and connectors to theend especially. Moreover, it is possible to maintain high detectingaccuracy which is approximately equivalent to the case of disposingterminals to anodes and cathodes of all of the cells, and to lower thetotal number of terminals to be approximately half thereof, compared tothe case of disposing terminals to anodes and cathodes of all of thecells, and hence it becomes possible to maintain the gaps between theterminals sufficiently, and thereby it becomes possible to connect theconnectors to the terminals smoothly. In addition, it is possible tolower increase of weight caused by the terminals as well as cost.

The sixth aspect of the present invention is the connecting structure,according to the fifth aspect of the present invention, in which theconnectors are connected to terminals of a fuel cell including a thirdcell (for example, the third cell 2 c in the embodiment) provided withno terminals at an anode and a cathode thereof, and the first cells orthe second cells which are stacked alternately.

According to the sixth aspect of the present invention, the third cellsare stacked alternately with the first cells or the second cells,thereby it is possible to reduce the number of the terminals which aredisposed to a fuel cell, to lower increase of weight and cost, whilemaintaining the necessary detecting accuracy.

The seventh aspect of the present invention is a fuel cell including:first cells provided with terminals to each of anodes and cathodesthereof, and second cells provided with no terminals to neither anodesnor cathodes thereof, in which the first cells are stacked from an endof an anode side in a stacking direction and the second cells arestacked from an end of a cathode side in a stacking direction,alternately.

According to the seventh aspect of the present invention, even if theparts which have nothing to do with power generation, such as dummyseparators, terminals, and connectors are not disposed on the endespecially, the cell voltages of both ends can be detected. Moreover, itis possible to maintain high detecting accuracy which is approximatelyequivalent to the case of disposing terminals to anodes and cathodes ofall of the cells, and to lower the total number of terminals to beapproximately half, compared to the case of disposing terminals toanodes and cathodes of all of the cells, and hence it becomes possibleto maintain the gaps between the terminals sufficiently, and thereby itbecomes possible to connect the connectors to the terminal smoothly. Inaddition, it is possible to lower increase of weight caused by theterminals as well as cost.

The eighth aspect of the present invention is the fuel cell according tothe seventh aspect of the present invention, in which the third cellsfrom neither anodes nor cathodes of which terminal are taken out arestacked with the first cell or the second cell alternately.

According to the eight aspect of the present invention, it is possibleto reduce the number of the terminals which are disposed to a fuel cell,to lower increase of weight and cost, while maintaining the necessarydetecting accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the principal part of a cell connectingapparatus equipped with a fuel cell and a voltage detecting connectorconnected to the fuel cell in one embodiment of the present invention.

FIG. 2 is a schematic sectional view of a cell which constitutes a fuelcell shown in FIG. 1.

FIG. 3 is a plan view of the first cell shown in FIG. 1.

FIG. 4 is a perspective view of the principal part the fuel cell shownin FIG. 1.

FIG. 5 is a sectional view of the principal part of a fuel cell and avoltage detecting connector connected to the fuel cell in the above.

FIG. 6 is a sectional view of the principal part of a cell connectingapparatus equipped with a fuel cell and a voltage detecting connectorconnected to the fuel cell in another embodiment of the presentinvention.

FIG. 7 is a schematic sectional view of a cell which constitutes a fuelcell shown in FIG. 6.

FIG. 8 is a plan view of a first cell and of a second cell shown in FIG.6.

FIG. 9 is a perspective view of the principal part the fuel cell shownin FIG. 6.

FIG. 10 is a sectional view of the principal part of a fuel cell or avoltage detecting connector connected to the fuel cell in the above.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the connecting structure to a cell of the voltage detectingconnector and fuel cell in one preferred embodiment of the presentinvention will be explained with reference to drawings.

FIG. 1 is a sectional view of the principal part of a cell connectingapparatus equipped with a fuel cell and a voltage detecting connectorconnected to the fuel cell in one preferred embodiment of the presentinvention. As shown in this figure, a fuel cell 1 is constituted from aplurality of cells 2 which are stacked in a predetermined numbers (inthis case, n). Each cell 2 is constituted by sandwiching a membraneelectrode structure 3 with separators 4 and 5.

The fuel cell 1 in this embodiment is equipped with first cells 2 a (2)in which terminals 6 and 7 for measuring voltage are disposed onseparators 4 on anode electrode 11 sides (refer to FIG. 2) andseparators 5 on cathode electrode 12 sides (refer to FIG. 2)respectively, and second cells 2 b (2) which have terminals 6 and 7 inneither the separators 4 nor the separators 5.

The first cells 2 a are disposed at both ends on a [+] polar side and a[−] polar side, and first cells 2 a and the second cells 2 b arealternately stacked from the both ends.

A cell connecting apparatus 10 is connected to the thus constituted fuelcell 1. The cell connecting apparatus 10 is equipped with apredetermined number of connectors 8 and 9, and can detect the voltageof the first cells 2 a to which terminals 6 and 7 are disposed, bycontacting the connectors 8 and 9 with the terminals 6 and 7 provided tothe first cells 2 a, respectively. As to the detection of the voltagesof the second cells 2 b, details will be mentioned later.

FIG. 2 is a schematic sectional view of a cell which constitutes thefuel cell shown in FIG. 1. As shown in this figure, the membraneelectrode structure 3 is equipped with a solid polymer electrolytemembrane 13, and an anode electrode 11 and a cathode electrode 12disposed on either side thereof.

A ring-like sealing member 14 is set at the periphery of the surfacewhere a pair of the separators 4 and 5, which are disposed on eitherside of the membrane electrode structure 3, are opposed to each other,and the solid polymer electrolyte membrane 13 is sandwiched by thesealing members 14. A fuel gas path 15, an oxidizing gas path 16, and acooling medium path 17 for supplying fuel gas, oxidizing gas, and acooling medium, respectively, are formed in both the separators 4 and 5.

FIG. 3 is a plan view of one of the first cells in this embodiment. Asshown in this figure, fuel gas penetrating holes 18 a and 18 b,oxidizing gas penetrating holes 19 a and 19 b, and cooling mediumpenetrating holes 20 a and 20 b are formed on both sides. In thesepenetrating holes, those on one side (left side in the drawing) serve assupplying ports 18 a, 19 a and 20 a, whereas those on the other side(right side in the drawing) serve as discharging ports 18 b, 19 b, and20 b. It should be noted that the separator may be formed by cuttingcarbon etc., and may be formed by press molding a metal etc.

Moreover, the terminals 6 and 7 disposed on the separators 4 and 5 ofthe first cell 2 a are, as shown in FIG. 4, formed at approximately thesame position, respectively, when they are looked at in the stackingdirection.

In the fuel cell 1 thus constituted, fuel gas (for example, hydrogengas) is supplied to the anode electrode 11 through the fuel gas path 15,and oxidizing gas (for example, air containing oxygen) is supplied tothe cathode electrode 12 through the oxidizing gas path 16. Then,hydrogen is ionized by the catalyst layer (not shown) of the anodeelectrode 11, and it moves to the cathode electrode 12 side through thesolid polymer electrolyte membrane 13. The electrons generated at thistime are taken out to the external circuit, and used as electricalenergy in a direct current. At this time, hydrogen ions, electrons, andoxygen react to produce water.

At this time, the electrodes which oppose to each other of the cells 2 aand 2 b which adjoin each other in the stacking direction have the sameelectrical potential. For example, as shown in FIG. 1, the electricalpotential Vk (1) of the cathode electrode 12 of the first cell 2 alocated at the first row of the end of the [−] pole side is equivalentto the electrical potential Va (2) of the anode electrode 11 of thesecond cell 2 b in the second row, which adjoins thereto.

In this way, the anode electrode 11 or the cathode electrode 12 of thesecond cell 2 b in the fuel cell 1 has an electrical potentialequivalent to that of the cathode electrode 12 or the anode electrode 11of the first cell 2 a which adjoins the second cell 2 b in the stackingdirection.

For example, the voltage V(n−1) of the second cell 2 b located in the(n−1)st row on the [+] pole side can be obtained as the differencebetween the electrical potential Va (n−1) of the anode electrode 11 ofthe second cell 2 b and the electrical potential Vk(n−1) of the cathodeelectrode 12. And the electrical potential of the anode electrode 11 ofthe second cell 2 b is equivalent to that of the cathode electrode 12 ofthe first cell 2 a located at the (n−2)th row, and the electricalpotential of the cathode electrode 12 of the second cell 2 b isequivalent to that of the anode electrode 11 of the first cell 2 alocated at the nth row. In other words, the electrical potential Va(n−1) is equivalent to the electrical potential Vk (n−2), whereas theelectrical potential Vk (n−1) is equivalent to the electrical potentialVa (n). Therefore, the electrical potential V (n−1) of the second cell 2b can be obtained as the difference between the electrical potential Vk(n−2) and the electrical potential Va (n).

Therefore, the voltage of the second cell 2 b with no terminals 6 and 7can be obtained from the electrical potential of the anode electrode 11or of the cathode electrode 12 of the first cell 2 a which adjoins thesecond cell 2 b in the stacking direction.

Moreover, in the fuel cell 1 of this embodiment, the first cells 2 a aredisposed at both ends of the [+] polar side and the [−] polar side, andthe first cells 2 a and the second cells 2 b are stacked from the bothends alternately, and hence it is possible to know certainly the voltageof the first cells 2 a which are disposed at both ends and the secondcells 2 b which adjoin the first cells 2 a in the stacking direction.Accordingly, substantially all of the cell voltages can be detected, andas a result, it is possible to maintain high detecting accuracyequivalent to the case of disposing the terminals 6 and 7 to the anodeelectrodes 11 or the cathodes 12 of all of the cells 2. In particular,when the total number of the cells is an odd number, it becomes possibleto detect all of the cell voltages by stacking the first cells and thesecond cells alternately.

When the total number of the cells is an even number, the first cellsare stacked exclusively at the center position, and thereby all of thecell voltages can be detected.

And since the total number of terminals 6 and 7 can be lowered to beapproximately half compared to the case of disposing terminals 6 and 7to the anode electrodes 11 or the cathode electrodes 12 of all of thecells 2, the gaps between the terminals 6 and 7 can be sufficientlymaintained, and it becomes possible to smoothly connect the connectors 8and 9 to the terminals 6 and 7, respectively. Furthermore, cost can belowered while preventing weight increase caused by the terminals 6 and7.

It should be noted that it is needless to say that the scope of thepresent invention is not restricted only to the above embodiment. Forexample, although in this embodiment it is explained taking the case inwhich the first cells 2 a which have terminals 6 and 7 are disposed atboth ends in the stacking direction, it is also possible to dispose thesecond cells 2 b at both ends.

In this case, it is necessary to insert a dummy separator into both endsto detect the cell voltage of the cells at both ends. Moreover, althoughthe terminals 6 and 7 having a projected shape are formed outside theend surfaces of the separators 4 and 5, respectively, to be insertedinto the connectors 8 and 9, respectively, it is also possible to formterminals having a groove shape inside the end surfaces of theseparators 4 and 5 such that the connectors can be inserted thereto, andfurther, the terminals may be formed integrally without changing theouter shape of the separators 4 and 5.

Moreover, in this embodiment there is explained a case in which thefirst cells and the second cells, which constitute the fuel cell, arestacked alternately ranging over the entirety of the line, but what isnecessary is that at least the first cells and the second cells arestacked alternately.

Hereinafter, the connecting structure to a cell of the voltage detectingconnector and the fuel cell in another preferred embodiment of thepresent invention will be explained with reference to the drawings.

FIG. 6 is a sectional view of the principal part of a cell connectingapparatus equipped with a fuel cell and a voltage detecting connectorconnected to the fuel cell in another preferred embodiment of thepresent invention. As shown in this figure, a fuel cell 101 isconstituted from a plurality of cells 102 which are stacked in apredetermined number (in this case, n) of cells 102. Each cell 102 isconstituted by sandwiching a membrane electrode structure 103 withseparators 104 and 105.

The fuel cell 101 in this embodiment is equipped with first cells 102 a(102) in which the terminal 106 for measuring voltage is disposed on aseparator 104 on an anode electrode 111 side (refer to FIG. 7), secondcells 102 b (102) in which the terminal 107 for measuring voltage isdisposed on a cathode electrode 112 side (refer to FIG. 7), and thirdcells 102 c (102) which have terminals 106 and 107 in neither theseparator 104 nor the separator 105.

A first cell 102 a is disposed at the end of a [−] pole side, and asecond cell 102 b is disposed at the end of a [+] pole side, and thefirst cells 102 a and the third cells 102 c are stacked alternately, thesecond cells 102 b and the third cells 102 c are stacked alternately,from each end.

A cell connecting apparatus 110 is connected to the thus constitutedfuel cell 101. The cell connecting apparatus 110 is equipped with apredetermined number of connectors 108 and 109, and can detect thevoltages of the anode electrodes 111 of the first cells 102 a and thevoltages of the cathode electrodes 112 of the second cells 102 b, bycontacting the connectors 108 with the terminals 106 disposed on thefirst cells 102 a, and by contacting the connectors 109 with theterminals 107 provided on the second cells 102 b, respectively.

FIG. 7 is a schematic sectional view of a cell which constitutes thefuel cell shown in FIG. 6. As shown in this figure, the membraneelectrode structure 103 is equipped with a solid polymer electrolytemembrane 113, and an anode electrode 111 and a cathode electrode 112disposed on either side thereof.

A ring-like sealing member 114 is set on the periphery of the surfacewhere a pair of the separators 104 and 105, which are disposed on bothsurfaces of the membrane electrode structure 103, oppose each other, andthe solid polymer electrolyte membrane 113 is sandwiched by the sealingmembers 114. A fuel gas path 115, an oxidizing gas path 116, and acooling medium path 117 for supplying fuel gas, oxidizing gas, and acooling medium, respectively, are formed in both the separators 104 and105.

FIG. 8 is a plan view of one of the first cells in this embodiment. Asshown in this figure, fuel gas penetrating holes 118 a and 118 b,oxidizing gas penetrating holes 119 a and 119 b, and cooling mediumpenetrating holes 120 a and 120 b are formed in both sides. In thesepenetrating holes, those on one side (left side in the drawing) serve assupplying ports 118 a, 119 a and 120 a, whereas those on the other side(right side in the drawing) serve as discharging ports 118 b, 119 b, and120 b. It should be noted that the separator may be formed by cuttingcarbon etc., and may be formed by press molding a metal etc.

Moreover, the terminals 106 and 107 disposed on the separators 104 and105 of the first cell 102 a are, as shown in FIG. 9, formed atapproximately the same position, respectively, when they are looked atin the stacking direction.

In the fuel cell 101 thus constituted, fuel gas (for example, hydrogengas) is supplied to the anode electrode 111 through the fuel gas path115, and oxidizing gas (for example, air containing oxygen) is suppliedto the cathode electrode 112 through the oxidizing gas path 116. Then,hydrogen is ionized by the catalyst layer (not shown) of the anodeelectrode 111, and it moves to the cathode electrode 112 side throughthe solid polymer electrolyte membrane 113. The electrons generated atthis time are taken out to the external circuit, and used as electricalenergy in a direct current. At this time, hydrogen ions, electrons, andoxygen react to produce water.

At this time, the electrodes which oppose each other of the cells 102 aand 102 b or of the cells 102 b and 102 c which adjoin each other in thestacking direction have the same electrical potential. For example, theelectrical potential of the cathode electrode 112 of the first cell 102a located at the first row of the end of the [−] pole side is equivalentto the electrical potential V of the anode electrode 111 of the thirdcell 102 c in the second row, which adjoins thereto. Moreover, theelectrical potential of the anode electrode 111 of the second cell 102 blocated at the nth row at the [+] pole side is equivalent to theelectrical potential of the anode electrode 112 of the third cell 102 clocated in the (n−1)th row, which adjoins thereto.

In this embodiment, since the third cells 102 c are stacked with thefirst cells 102 a or the second cells 102 b alternately, it is possibleto obtain the electric potential difference between two cells whichadjoin each other (for example, the first cell 102 a and the third cell102 c, or the second cell 102 b and the third cell 102 c). Therefore, itbecomes unnecessary to dispose a dummy separator, a terminal, or aconnector especially, which is not related to power generation, and thecell voltage of both ends can be detected, while lowering the number ofparts, cost, stacking width, and increase in weight.

Since the total number of terminals 106 and 107 can be lowered to beapproximately ¼ compared with the case of disposing terminals 106 and107 on the anode electrodes 111 or the cathode electrodes 112 of all thecells 102, the gaps between the terminals 106 and 107 can besufficiently maintained, and it becomes possible to connect smoothlyconnectors 108 and 109 to the terminals 106 and 107, respectively.Furthermore, cost can be lowered while preventing the weight increasecaused by the terminals 106 and 107.

It should be noted that, needless to say, the scope of the presentinvention is not restricted only to this embodiment. In this embodiment,although there is explained a case in which the third cells are stackedwith the first cells or the second cells alternately, the number of thethird cells can be increased or decreased, corresponding to the requireddetecting accuracy. For example, it is possible to constitute the fuelcell from the first cells and the second cells, without using the thirdcells. In this case, when the first cells are stacked from one end ofthe fuel cell, whereas only the second cells are stacked from the otherend of the fuel cell, it is possible to detect all of the cells bydisposing cells which are equipped with terminals at both the anode andthe cathode thereof at the center portion. Moreover, although theterminals 106 and 107 having a projected shape are formed outside theend surfaces of the separators 104 and 105, respectively, to be insertedinto the connectors 108 and 109, respectively, it is also possible toform terminals having a groove shape inside the end surfaces of theseparators 104 and 105 such that the connectors can be inserted thereto,and further, the terminals may be formed integrally without changing theouter shape of the separators 104 and 105.

According to the first aspect or the third aspect of the presentinvention, while detecting substantially all of the cell voltages, thegap between terminals is maintained, thereby preventing weight increasecaused by the terminals, and increase in cost.

According to the second aspect or the fourth aspect of the presentinvention, the detecting accuracy of the cell voltage can be maintainedat a level equivalent to the case of disposing terminals to the anodesand the cathodes of all cells. Moreover, it becomes unnecessary todispose things like a special dummy cell by disposing the cell which hasterminals at both ends thereof.

According to the fifth aspect or the eighth aspect of the presentinvention, the cell voltages of both ends can be detected, whilelowering the number of parts, cost, stacking width and increase inweight.

According to the sixth aspect or the seventh aspect of the presentinvention, while maintaining the detection accuracy required, the numberof terminals which are disposed on a fuel cell can be reduced further,thereby lowering the increase in weight and cost further.

1. A connecting structure, comprising: a connecting apparatus havingconnectors; and a fuel cell stack having a [−] pole side and a [+] poleside, the fuel cell stack including a plurality of first cells disposedat an end of the [−] pole side and stacked in a stacking direction ofthe fuel cell stack, each of the first cells having an anode terminalfor detecting cell voltage, the anode terminal provided only to a [−]pole side of the first cell, and a plurality of second cells disposed atan end of the [+] pole side and stacked in the stacking direction of thefuel cell stack, each of the second cells having a cathode terminal fordetecting cell voltage, the cathode terminal provided only to a [+] poleside of the second cell; wherein the connecting apparatus and the fuelcell stack are electrically connected by contacting the anode andcathode terminals with the connectors, said connectors disposed atpositions corresponding to the anode and cathode terminals.
 2. Theconnecting structure according to claim 1, wherein the fuel cell stackfurther comprises a plurality of third cells, each of the third cellsprovided with no terminals for detecting cell voltage at an anode and acathode thereof, at least one of the third cells being stackedalternately with the first cells, and at least one of the third cellsbeing stacked alternately with the second cells.